A basic wireless charging system may include a wireless power transmitter unit (PTU) and a wireless power receiving unit (PRU). For example, a PTU may include a transmit (Tx) coil, and a PRU may include receive (Rx) coil. Magnetic resonance wireless charging may employ a magnetic coupling between the Tx coil and the Rx coil. In some cases, a PRU may be implemented in a computing device, such as a mobile computing device, that can be placed on a charging mat including a PTU. In some cases, magnetic field uniformity design goals may drive PTU coil design toward a high number of closely spaced turns and relatively higher energy loss when transferring power between PTU and PRU coils, while for large separation between a PRU and a PTU in a direction perpendicular to a surface of the PTU may require a minimum coil coupling efficiency, driving design of PTU coil toward less turns with large spacing for lowest energy loss when transferring power between PTU and PRU coils.
The same numbers are used throughout the disclosure and the figures to reference like components and features. Numbers in the 100 series refer to features originally found in FIG. 1; numbers in the 200 series refer to features originally found in FIG. 2; and so on.